1. Field of the Invention
The present invention relates to slide fastener (e.g., zipper) continuous element row manufacturing and more particularly to an improved apparatus for manufacturing slide fastener coil-shaped continuous element row.
2. Description of Related Art
A coupling head forming portion of a conventional apparatus for manufacturing slide fastener continuous element row is disclosed in U.S. Pat. No. 6,302,676, as shown in FIGS. 17-20. The apparatus comprises a pair of screws 1, a die 2, a coupling head forming disc 3, a mandrel 4 between the die 2 and the forming disc 3, a core thread 5 received in a longitudinal recess of the mandrel 4, and an element 6 received in a space defined by the die 2 and the coupling head forming disc 3, the element 6 having a joint portion 6a and an coupling head 6b formed by the coupling head forming disc 3.
An upper leg portion forming portion of the apparatus is shown in FIG. 19. It further comprises a rotary hammer 7 having an inclined peripheral surface 7a proximate a core thread guide groove 6c while operating. The element 6 is stitched to a fabric. However, the seam may be disengaged from the core thread guide groove 6c because the core thread guide groove 6c is open.
However, the prior art suffered from several disadvantages due to undesirable constructions of the screw 1 and the die 2. For example, the diameter of the screw 1 is limited such as between 6.5 mm and 8 mm. As such, a diameter of a shaft 3a of the coupling head forming disc 3 is also limited. Otherwise, there is a possibility of interference between the shaft 3a and the screw 1 at either side of the coupling head forming disc 3. Hence, the coupling head forming disc 3 may vibrate strongly due to a high forming pressure and rotation of the coupling head forming disc 3 in the manufacturing process of the element 6. In brief, a strength of the shaft 3a is not sufficient. Further, if sizes of all of the screw 1, the die 2, and the coupling head forming disc 3 are increased, the necks 2a may become sharp (i.e., smaller cross-sections) for conforming with the diameters of the screws 1. This can reduce a contact area in the manufacturing process of the element 6. In response, the joint portion 6a of the element 6 may recess (i.e., deformed). Furthermore, a precision of the element 6 may be adversely affected because a size of the mandrel 4 is small and the mandrel 4 tends to wear (i.e., size changed) or the size of the mandrel 4 exceeds an allowance due to machining error. At this time, an appropriate adjustment of locations of the necks 2a, the mandrel 4, and the coupling head forming disc 3 is required. However, such adjustment is very difficult because the necks 22 are integral part of the die 2 and the coupling head forming disc 3 rotates about the shaft 3a. Moreover, as shown in FIGS. 18 and 20, the element 6 thus produced by the prior art has a slightly arcuate bottom side 6d. Hence, a point contact is formed as the element 6 is stitched to the fabric 8. In other words, both contact area and friction are small. As such, the element 6 tend to slip (i.e., displace) in use. In response, the seam may be displaced. Thus, it is desirable to provide an improved apparatus for manufacturing slide fastener coil-shaped continuous element row in order to overcome the above drawbacks of the prior art.
It is an object of the present invention to provide an apparatus for manufacturing slide fastener coil-shaped continuous element row wherein a rear forming assembly is secured to a rear abutment plate, the rear forming assembly being operable to stably perform a lateral or axial adjustment of the apparatus so as to provide an optimal zipper forming space defined by front and rear abutment plates, screws, and a mandrel. Thus, high quality products are manufactured.
In one aspect of the present invention, a fine adjustment is made in rear of an abutment assembly so that the adjustment is made easy and simple.
In another aspect of the present invention, once the element has been stitched to a fabric, a seam will be prevented from disengaging because it is protected by an arcuate recessed portion formed on a top side of the element.
In still another object of the present invention, both contact area and friction between the element and the fabric can be increased significantly by the provision of flat area formed on a bottom side of the element when a flat piece of the bottom shuttle assembly is abutted on the element.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.